I thought I'd give those interested in this a little heads up if you haven't already checked the parts. There are a couple of parts which may or may not give you problems in this project.

First, there is a 74C14 HEX SCHMITT INVERTER. The original part seems to be discontinued, but NTE makes a replacement. I will try this in the prototype to make sure it works. This seems to be in stock at Mouser, but only about 700 (as of today) in stock.

The 2N5172 and PN5138 are apparently at their end of life. Mouser still has a pretty good stock. I don't think these aren't really critical. Any decent small signal NPN or PNP should work.

There is a matched pair in the VCO or course. This can be a hand matched pair, or any of the usual monolithic pairs. The pinout will most easily fit an EBC type pinout, so a typical monolithic pair like SSM2210, LS318, MAT-12 should work great. You can shoe horn the 2N5172s, but you will have to pretzel the leads to fit since the 5172 is an ECB pinout.

The JFET is a 2N5246. Still out there, but at its end of life. Again Mouser has a bunch, but not really huge numbers.

If anyone can find a 2 Meg pot, please tell me. You will need to substitute 1 Meg for these two pots in the EG.

Last, these aren't gone, but might be problematic depending on where you are. It takes two Vactrols, VTL5C3/2. I've seen them in a couple of places.

Anyway, just a quick heads up to make sure you can source the parts you want to use if you are going to build this.

I'm attaching a very PRELIMINARY BOM. This will almost certainly change, so don't buy off this. I offer it for information only.

The 74C14 should be replaceable with a common 40106. The motorola ICs I have are marked with both MM74C14N and CD40106BCN.

cheers,
Dave

Yeah, I'm sure that's right.

Nyle told me once he never wanted a design to depend on a "special" component. One that might go out of production which is why he never designed with the chips others were using. That's one of my favorite things about his design. It was very easy to resurrect them because the components are still made with only one or two exceptions and those aren't too hard to find either.

A little more progress. the prototype PCBs came in this last week. I have already made changes/corrections to the layout, but I can still stuff these to verify the basic function. I'll post progress when I've got something to share.

Sorry to seem dormant. I've pretty much finished the Steiner Duophonic keyboard stuff and can make more time for the Microcon. I will have the version 1.1 prototype PCB next week and will post results after I get one built.

Brief update. The prototype is stuffed and I passed it off to Nyle today. I thought it best to let him put it through its paces because he knows much better than I how it should work. I'll let you know how it goes._________________David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

Brief update. The prototype is stuffed and I passed it off to Nyle today. I thought it best to let him put it through its paces because he knows much better than I how it should work. I'll let you know how it goes.

Well, that was fast. Nyle got it up and working. I only had one bad signal error. I guess I'd better finish a panel.

1. He has some notes he made "in the day" regarding a mod to make it more compatible with his EVI wind controller and asked me to hold off on the PCBs until he had a chance in the next couple of days to look into it. Something about the sustain in the EG section.

2. I asked about the 15 volts, and he echoed what I hope I've said here and elsewhere that it should work without a problem, but some of the transistor biasing resistors may need to be changed. Bless him, he doesn't have a 15 volt supply to test the prototype, so I'm going to give him one next week and he'll test in on 15 volts.

I'll make sure I order plenty of PCBs. If I run out, I'll order more, so don't worry.

First cut at a panel will all the pots, switches, trimmers on the front panel. I'm sure it could be condensed, but I'm trying to keep the look and feel of the original Synthasystem panels, the resurrected panels I did, and the Microcon panel.

OK. I've ordered a bunch of PCBs. I am not formally taking orders, I want to build one more and make sure the changes I made didn't screw up anything. I added standard power supply connectors to the PCB, made the pot and switch connectors consistent, and I added a summing resistor and pad if you want to play around with adding a VC pulse width input.

Read the notes on the schematic for some comments about the various switches, pots, and trimmers. I've also redone the panel layout (I'm not posting the FPD file yet until I order a panel and am sure everything fits.)

Right now pricing for the PCBs will be $20.00 for a single PCB with some kind of discount for multiple PCB orders to be determined.

I received what I hope will be the production PCBs for the Microcon. I stuffed one and gave it to Nyle to test. He should be through with it within a week or so. Then, I'll be ready to sell the PCBs, so please stay tuned. The initial tests on the last prototype were great. Nyle found some layout errors and made some suggestions which are reflected in the latest layout.

See below for the documentation packet.

Read the notes because there are choices to be made regarding the trimmers, panel pots, and the Sustain and Resonance (Q) switches.

I apologize I've been ignoring the list. I'll try to answer questions:

The PCB is 4.0 by 3.9 inches. The panel design I did includes all the options and is generous on space. If you mount the PCBs at a right angle to the panel, don't use all the panel control options, and put panel parts closer together, you could cut the width down. The unit draws -10mA and +20mA

Details:
Price will be $30.00 for a single unit, $20.00 for each additional PCB. I have 50 in stock and if those sell out (probably not), I will simply order more

PayPal is accepted at the email in my signature. Docs are a little "thin" right now, but I'll send what I have and will try to be fast in responding to all questions.

Double check the parts list attached to make sure you can source the parts. nothing too weird other than the Vactrols and 74C14 schmitt trigger and there are some good substitutes.

Check the website under the Synthasystem Price List for shipping costs.-

I shipped the order of everyone who has sent money as of today 11/24/2012, (except one who asked me to wait til after Thanksgiving) So, the US orders should be there Monday or Tuesday. The one U.K. order may take a week or so. Please let me know if there are any problems with your order.

So, I've been trying to get mine up and running - and aside from trouble getting parts, which I have more or less worked around, I have a couple of questions.

I chose to ground all pots and jacks that needed it on the front panel instead of attaching all of the flying wires. I checked continuity between pads on the board and ground to figure out what needed to be grounded. This may be the source of part of the problem I'm having. On the schematic, it looks like all 2M pots (attack,decay,lfo rate) are used as variable resistors, and don't have one pin grounded like they would if they were dividers. On the board, their third pin is grounded. Which way should it be?

I also ran into problems because the only advice on switch wiring is "pins 3 and 6 up". Unfortunately, I didn't look at the schematic to see that pin 1 is the actual switch pin, and wired mine 3-2-1 top to bottom (lazy).

I'm pretty sure that they should be wired like this:
3 UP
1
2

and for the LFO
3 6 UP
1 4
2 5

DAMP has a mistake according to an email I got, is this right?
3 6 UP
2 4
1 5

So, I've been trying to get mine up and running - and aside from trouble getting parts, which I have more or less worked around, I have a couple of questions.

I chose to ground all pots and jacks that needed it on the front panel instead of attaching all of the flying wires. I checked continuity between pads on the board and ground to figure out what needed to be grounded. This may be the source of part of the problem I'm having. On the schematic, it looks like all 2M pots (attack,decay,lfo rate) are used as variable resistors, and don't have one pin grounded like they would if they were dividers. On the board, their third pin is grounded. Which way should it be?

I also ran into problems because the only advice on switch wiring is "pins 3 and 6 up". Unfortunately, I didn't look at the schematic to see that pin 1 is the actual switch pin, and wired mine 3-2-1 top to bottom (lazy).

I'm pretty sure that they should be wired like this:
3 UP
1
2

and for the LFO
3 6 UP
1 4
2 5

DAMP has a mistake according to an email I got, is this right?
3 6 UP
2 4
1 5

-gerald

Hi Gerald,

Thanks for asking this on the list so everyone who is interested can benefit. But also remember you can always send me email directly if you want. You might get a faster response as I don't look at the list too often anymore.

POTS:
First, I don't see a problem grounding through the panel. So long as you get a good ground and don't experience ground loops, it's fine.

There are a couple of pots which are variable resistors as you note. But, the third pins on these pots are not grounded on the PCB. There are three pads on the connector because of the part pattern I use, but one pad on the end is not connected. DO NOT GROUND THE OTHER END OF THE POT.

I used Eagle to do the schematic and PCB layout and Eagle will not connect a pin arbitrarily to any net on the PCB layout unless it is connected on the schematic. So, the pins which are not connected on the schematic on these pots are not connected on the PCB.

Also, for these pots, there is an option to have a trimmer on the PCB OR a pot on the panel, do not install both the trimmer and pot. Look at the schematic for more info.

SWITCHES:
I apologize for using non-standard numbering on the switches. I numbered them this way looking at the back of the switch, paddle motion is up and down:

SPDT:
2
1
3

Where:
2 - one end of a SPDT switch, one of two throws
1 - middle pin on the SPDT switch, the pole
3 - the other end of the SPDT switch, the other throw

Which way is "up" depends on how you label your panel.

DPDT:
2 5
1 4
3 6

Where:
2 - throw on one end 5 - throw on same end as 2
1 - pole, middle 4 - pole, middle pin
3 - throw on other end 6 - throw on same end as 3

So for the Beat/Vibrato switch (you call it the LFO switch, right?) referring to the schematic you would connect the middle pin of one side of the switch to the pad labeled "1" on the PCB at the connector location. Connect the other middle pin to the pad labeled "4". Pick an end of the switch, it doesn't matter right now which one. These two pins on the switch become pins "2" and "5". "2" is on the same side of the switch as "1" and "5" is on the same side as "4"

Back of DPDT:
2 5
1 4
3 6

Connect a wire from pin "2" on the switch to the PCB "2" location and "5" on the switch to "5" on the PCB.

On the other side of the switch, connect "3" to "3" and "6" to "6".

When the switch is flipped so that pole "1" is connected to throw "2", pole "4" should be connected to throw "5". This is the "Vibrato" position. When pole "1" is connected to throw "3" and pole "4" is connected to throw "6", this is the "Beat" position.

Now, for the "Damp" switch. Originally, when pole "1" was connected to throw "2", pole "4" was connected to throw "5" (throw "5" is not connected to anything). This resulted in unintended behavior in the EG section. The fix is to simply reverse the throws on one side of the switch. I choose the following:

Wire the side of the switch going to pole "4" as indicated. Pad "4" on the PCB to the middle, then pads "5" and "6" on either side of the middle on one side of the switch. Now, instead of using the above numbering for a DPDT switch, use the following numbering ON THIS SWITCH ONLY. Use the numbering on the PCB as it is.

3 5
1 4
2 6

That is, the wire from pad "3" on the PCB needs to go to the same end of the switch as the wire from pad "5" (as opposed to throw "6") and "2" goes to the same end of the switch as the wire from pad "6" (as opposed to throw "5").

If memory serves, the "Damp" function is active when the poles of the switch, "1" and "4", connect to the throws on the end of the switch which connect to pads "2" and "6" on the PCB. In the above diagram, the paddle would be in the "up" position connecting "1" and "4" to "2" and "6" respectively (remember, paddle up connects to the pins on the bottom of the switch, paddle down connects to the pins on the top of the switch, just to be more confusing). When the "Damp" is active, the EG will rapidly drop to zero when the gate/trigger is removed. so, if you are triggering the EG with a very short trigger pulse, you may not hear anything.

If this is still confusing, let me know and I'll do what I can to help make it clear.

A couple of useful tweaks. Since the board is faithful, the "extra knobs" have limited useful range. Here's how to make two of them 100% useful.

Resonance - (Q Set). Put an extra 10k inline, directly on the pot - either lug is fine. This keeps it from going totally nuts until it's almost all the way up, and it also reduces the unwanted resonance at its lowest value.

PW (SQ duty). Put two 25k pots inline, one between CW/Ground and the other between -12V and CCW. This makes the knob useful over its full range.

As noted - the Microcon has kindof a west-coast style vactrol based low-pass gate style VCA. This means that you have to turn the filter down to make the envelope functional.

The 2M attack/decay pots have really long time constants for most of their range. Punchy/fast values are within ~30degrees from zero. A log pot might work better for both. Of course, you might need a hard to find reversed-log pot- not sure on this.

I tuned mine up with a minibrute - and the microcon tracks nicely and adds a very useful second oscillator/filter/VCA combo! Sounds pretty great. I only had to use the VC Trim pot to get it tracking in tune (amazing since I threw some BC547's I had lying around in in place of the MAT02/SSM). Not sure I could tell what the HF track trimpot does - it's subtle?

One of the two CV inputs (VC2) for the oscillator frequency bypasses the VC trimpot... meaning it won't track in tune. Ahhh... maybe I AM supposed to use HF track somehow... may have to revisit this.

The pulse/beat switch seems to invert the pulse-width, i.e. 10% becomes 90% duty cycle. Since the knob can do this too, maybe it isn't necessary?

Beat seems to add an out-of-phase sawtooth to the main sawtooth that "beats" with it.

I'm running mine off of an +-15V frac supply. I added 12V regulators where the ferrite beads are supposed to be.

A couple of useful tweaks. Since the board is faithful, the "extra knobs" have limited useful range. Here's how to make two of them 100% useful.

Resonance - (Q Set). Put an extra 10k inline, directly on the pot - either lug is fine. This keeps it from going totally nuts until it's almost all the way up, and it also reduces the unwanted resonance at its lowest value.

PW (SQ duty). Put two 25k pots inline, one between CW/Ground and the other between -12V and CCW. This makes the knob useful over its full range.

As noted - the Microcon has kindof a west-coast style vactrol based low-pass gate style VCA. This means that you have to turn the filter down to make the envelope functional.

The 2M attack/decay pots have really long time constants for most of their range. Punchy/fast values are within ~30degrees from zero. A log pot might work better for both. Of course, you might need a hard to find reversed-log pot- not sure on this.

I tuned mine up with a minibrute - and the microcon tracks nicely and adds a very useful second oscillator/filter/VCA combo! Sounds pretty great. I only had to use the VC Trim pot to get it tracking in tune (amazing since I threw some BC547's I had lying around in in place of the MAT02/SSM). Not sure I could tell what the HF track trimpot does - it's subtle?

One of the two CV inputs (VC2) for the oscillator frequency bypasses the VC trimpot... meaning it won't track in tune. Ahhh... maybe I AM supposed to use HF track somehow... may have to revisit this.

The pulse/beat switch seems to invert the pulse-width, i.e. 10% becomes 90% duty cycle. Since the knob can do this too, maybe it isn't necessary?

Beat seems to add an out-of-phase sawtooth to the main sawtooth that "beats" with it.

I'm running mine off of an +-15V frac supply. I added 12V regulators where the ferrite beads are supposed to be.

There is a simple correction I encourage you all to do in order to fully enjoy the Microcon as it should operate.

Short version. I was meeting with Nyle a while back about several things and one was the Microcon. The result is Nyle noticed his original hand drawn schematic had a “typo”. The fix is simply swapping two wires on the back of the DAMP switch then rotating the switch on the panel.

What should happen is when the DAMP switch is on, the EG rapidly decays when an incoming gate/trigger terminates. That is, the EG total duration is defined by the length of the incoming gate/trigger. When the DAMP switch is off,the EG will complete the minimum cycle defined by the setting of the ATTACK and DECAY knobs. If the gate/trigger lasts longer, the EG decays to the SUSTAIN level and stays there until the gate/trigger is terminated, then it decays to zero.

Right now, the way it is wired, the EG always terminates when the trigger is terminated. This is incorrect behavior.

EASY VERSION
Assuming you have the switch wired properly to start with, simply swap the two wires which connect to pins 2 and 3 on the PCB connector and then rotate the switch 180 degrees. You can do this on the switch or on the PCB whichever is easier. (Alternately, you can swap the wires going to pins 5 and 6 on the other side of the switch.)

If you have any questions or problems, please let me know and I’ll do what ever I can to help you. If you need a step by step, please don’t hesitate to write.

If you haven’t built yours yet, I encourage you to push it up on your stack! This is really an incredibly fun module with a very interesting character and behavior.

Some characteristics to note:
1. The VCF also acts as a gain of sorts. I suggest you turn it fully CCW, then slowly CW until you just hear a sound with a gate absent. When you hit it with a gate, you will get a nice sweeping filter effect.
2. Remember, the EG is hardwired into the VCF cutoff and VCA, so you will always get a filter sweep the depth depends on where you initially set the VCF knob.
3. The Resonance is really sensitive. If you go much more than half way, the self resonance is loud and crazy, be careful.
4. The LFO knob is backwards on purpose. Nyle didn’t have any reverse log pots and he wanted better control at higher frequencies, so he wired the pot backwards. Really this is true, he just told me yesterday.
5. Remember the calibrated CV input is also hardwired into the VCF cutoff frequency so it always tracks.
6. As with all analogue gear, there is no right/wrong way to use it. Just have fun with it.

Have fun guys. Please let me know how it goes.

The PCBs are fine, it's just the switch wiring that needs to be corrected._________________David M. Ingebretsen, M.S., M.E.
Collision Forensics & Enginering, Inc.

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot vote in polls in this forumYou cannot attach files in this forumYou can download files in this forum

Please support our site. If you click through and buy from our affiliate partners, we earn a small commission.